The invention relates to a chain shackle for fastening the end of a hoist chain of a chain hoist to a hoisting member or the chain hoist, the hoist chain comprising chain loops fastened to each other with the planes formed by the adjacent chain loops mainly at a 90° angle to each other.
In chain hoists, the end of the hoist chain must be locked in two places depending on the implementation of the hoist. In single-chain hoists, a chain shackle is necessary in the hook cylinder of the hoisting hook. In a double-chain hoist, the end of the chain needs to be locked in the frame of the chain hoist. In addition, a type of lock piece is needed in the chain bag to operate a limit switch and/or prevent the chain from being run out of the chain hoist completely. Often all three places have their own locking elements.
A general manner of locking the chain to the hook cylinder and chain hoist frame is to use a pin that passes through the chain loop and supports itself against the hook cylinder and chain hoist frame. The pin solution has the problem that the pin is a double-supported “beam” subjected to bending and its tension level becomes high because it is not possible to push a pin with a very large diameter through the chain loop. In addition, during chain change, the pin may be set in a different position than originally. The direction of the load of the pin may then become disadvantageous so that the side of the pin that was originally subjected to compression is now subjected to tensile stress. Especially if a notch has formed in the pin during compression by a chain loop, the pin solution becomes dangerous. In the pin solution, the surface pressure between the chain loop and pin is disadvantageous due to the geometrics, because, in principle, it is a point contact.
Often shape-locking elements are used in locking the chain, either directly moulded into the hook cylinder or to separate parts that in turn lock into the hook cylinder or chain hoist frame by shape-locking.